Process for utilizing waste vegetable material



y 1937. R. B. ARNOLD 2,080,454

PROCESS FOR UTILIZING WASTE VEGETABLE MATERIAL Filed Nov. 10, 1952 6Sheets-Sheet 1 May 18, 1937. R. B. ARNOLD 2,080,454

PROCESS FOR UTILIZING WASTE VEGETABLE MATERIAL Filed Nov. 10, 1932 6Sheets-Sheet 2 INVENTOR ATTORNEYS May 18, 1937. R. B. ARNOLD PROCESS FORUTILIZING WAS TE VEGETABLE MATERIAL e Shets-Sheet a QN m \h I N 1 3 m m\h N m h L. :1 E 1 kh k n N NW. iwh &* m 1 i m 1w Y? Filed Nov. 10, 1932BYWK%@ ATTORNEYS May 18, 1937. R. B. ARNOLD PROCESS FOR UTILIZING WASTEVEGETABLE MATERIAL Filed Nov. 10, 1952 6 Shets-Sheet 4 g' INVENTOR 4%ORNEYS y 1937- R. B. ARNOLD 2,080,454

PROCESS FOR UTILIZING WASTE VEGETABLE MATERIAL Filed Nov. 10, I952 6Sheets-Sheet 5 INVENTOR BY W AITORNEYS May 18, 1937. R ARNOLD 2,080,454

PROCESS FOR UTILIZING WASTE VEGETABLE MATERIAL Filed Nov. 10, 1932 6Sheets-Sheet 6 LIME SOLUTION WASTE TOBAQCO NICOTINE HEAT TO DRIVE OFFNICO'TINE DRIED TOBACCO REslDuEs GASES AND VAPOR l I VAPOR TOWER or C014 v PRE-CONCENTRATION ETC EVAPORATING co VAPORS AND DES R C E APPARATUSAPPARATUS ETC GASES 8\ D]ST)LLAT|ON FINE DUST F il SOLIDS II) oPOTASSIUM SALTS 5 CENTR'FUGE AND SOLIDS 9 l SEMI QuENcH SOLIDS WATERPOTASSIUM SALTS EXTRACTING SETTLING TANKOF PRE-CONCENTRATION ANDHYDROXIDE F APPARATUS APPARATUS SOLUTION WET SOLID CARBON AND CALCIUMcARaoNATE WATER HOT cAsEs PRE DRYER CALCIUM DRY SOLID cARBo OXIDE FINALBURNER AND CALCIUM CARBONATE CAUSTIC LIIAAE CASE: HARDENING I COMPOUND EINVENTOR BY K U' A1 -ro Patented May 18, 1937 UNITED STATES PATENTOFFICE PROCESS FOR UTILIZING WASTE VEGETABLE MATERIAL ware ApplicationNovember 10, 1932, Serial No. 642,011

3 Claims.

This invention relates to a process for utilizing waste vegetablematerial. The invention more particularly relates tothe recovery ofvalues from waste vegetable material derived from landplants which whentreated as hereinafter described will evolve a relatively highproportion of volatile, combustible materials and which are relativelyhigh in potassium compounds. A typical. waste material of this kind iswaste tobacco residue. There are some other vegetable materials. towhich the process is applicable, such, for example, as cotton hulls.

One of the principal obiectsof the present invention is to provide aprocess which will enable a nicotine extraction plant to recover fromits residues of tobacco material, after the extraction of the nicotine,the alkaline material which, of necessity, is used in the process ofextracting nicotine, and at an. economical cost.

A further object of the invention is to recover from the said residuesthe potash content at a cost which will be commercially economical.

With these general objects in. view and others which will be obvious tothose skilled in the art from the description hereinafter, the inventionconsists in the features which will be more fully pointed outhereinafter.

In the accompanying drawings is illustrated an apparatus which may beused in carrying out the invention. In these drawings:

Figs. 1 and 1a together constitute a diagrammatic plan view of theapparatus.

Fig. 2 a diagrammatic side view partly in section, on the line 2-4, Fig.1.

Fig. 3. a similar View on the line 3-3, Fig. 1.

Fig. 4 asimilar view on the line 44, 1A.

Fig. 5 a transverse section on the line 5-5, Fig. 1.

Fig. 6 a transverse section on the line 6--6-, Fig. l. i

Fig. 7 a diagrammatic side view partly in section of the preliminaryconcentration: apparatus.

Figs. 8, 9, and 10' horizontal sections on the lines il-S, 9--9, andilllli, respectively, of- Fig. '7.

Fig. 11 a detail vertical section, partly in elevation, to illustratethe quenching apparatus, and

Fig. 12 a flow sheet to illustrate more fully the steps of the processin their relative order.

It has been common in the art heretofore to recover some of the valuesfrom waste tobacco material, for example, nicotine and ammoniaaccompanying it, the nicotine and ammonia being recovered usually as.sulphates. In order to free 5 the nicotine from the waste tobaccomaterial it is usual to comminute the tobacco material and then treat itwith a solution of an alkaline material, usually lime water, and subjectit to what may be termed a low temperature steam distillation. As aresult of this treatment, the tobacco residue, freed of its nicotine andammonia, as well as of practically all its moisture, is obtained in asubstantially dry condition. The alkaline material supplied to thetobacco to release the nicotine remains with the" residues.

It has been recognized that the dried residues from the nicotineextraction plant have an agricultural value, not only on account of thealkaline earth compounds and a small amount of nitrogen, but also andmore particularly because of the alkali compounds, particularly potash,carried by the residues. However, the quantity of such dried residue isso great and the cost of transportation is so high because of its bulkthat there is difficulty in disposing of such residues for agriculturalpurposes at a price such as to lower the cost of making nicotine.

Many attempts have been made to recover the values from plant refuse,such as tobacco waste, and some other plant material, but withoutcommercially successful results. It has been found that the tobaccoresidues are exceedingly difficult to burn. When fired in small piles inthe open air they can finally be burned to ashes, but in the attemptswhich have heretofore been made to burn them in retorts or furnaces ithas been considered necessary to combine some additi'onal fuel, such asfine coal, with the refuse in order to burn them in furnaces ofreasonable capacity, or to use fuel to heat the retorts externally.

On account of the cost of such methods of burning it has usually beenthe practice, in disposing of such plant refuse, to attempt to recovernot only the potash but also volatile products which are evolved in theburning, in the same way that pyroligneous acid is derived in theburning of wood to charcoal and then worked further to separatelyrecover the various organic chemicals.

These attempts, as far as known to me, have not proved commerciallysuccessful, because of the necessary investment in the apparatusrequired, and the low and uncertain market value of the productsobtained from the volatiles. Owing to the inability by priormethods toobtain complete carbonization of the potassium compounds there is alsopresent in the final product a small percentage of potassium hydroxide,as well as some potassium cyanide formed by the combination of the fusedpotassium carbonate with the carbon and nitrogen. This makes itnecessary to treat the potassium compound or the solution of the same byfurther steps in order to remove the potassium cyanide, because it is adangerous ingredient in the product on account of its highly poisonousnature. Applicant has discovered that by abandoning any attempt to savethe volatile products of the destructive distillation of the tobaccoresidues, as a base for the recovery of organic chemicals and using apart of those volatile products which are combustile as fuel directly ina. kiln containing the tobacco residues, with a restricted access ofair, and burning all the remainder of such volatile combustiblesimmediately on their escape from the kiln without permitting them tocool essentially, and with sufficient air to complete the combustionWithout undue cooling of the products of combustion, the heat valuethereby developed in the two stages is not only more than suiiicient tocarry on the destructive distillation of the residues at the first stageto the point of obtaining a good porous fixed carbon product in whichthe inorganic compounds are well disseminated, but is sufficient tocarry the combustion of the combustible volatiles to completion andleave an excess of heat in the second stage which will more than sufliceto carry out the concentrating and evaporating operations necessary inrecovering the alkali compounds in solid form. The fixed carbon residueforms a concentrated product of sufficient value for agriculturalpurpose to allow it to be sold at a profit, and in addition is good as astarting material to be extracted with water for the recovery of thepotassium and sodium compounds. After extraction the solid residueconsisting of the fixed carbon and the alkaline earth compounds,particularly calcium carbonate, not only has a marketable value foragricultural purposes, but can be dried and burned to convertpractically all of such carbonates into oxides, the fixed carbon havingsufficient heat value to burn the carbonates to oxides and to dry thewet material coming from the extracting apparatus before it enters thecalcining kiln.

A further and most important feature of the invention consists insimultaneously concentrating the alkali solution from the extractionstep and converting any caustic portion thereof into carbonate by thedirect contact of the solution with the hot gases relatively rich in CO2produced by the complete combustion of the combustile volatile productsescaping the destructive distillation kiln as hereinbefore described. Asthis step of the process can be conducted in an apparatus which ishighly resistant to chemical action and yet not expensive, as forexample a scrubbing tower whose exposed parts are chemical brick, itbecomes commercially possible to carbonate the caustic alkali andthereby produce a marketable solid salt free from objectionabledeliquescent and caustic ingredients, and also free from the dangerouspotassium cyanides.

It is an important advantage of the present invention that the calciumof the lime used in treating the tobacco as aforesaid is recovered in adesirable form either as a carbonate, under one method of treatment, oras an oxide under another method of treatment, in accordance with theinvention. When recovered as an oxide, it may again be used fortreatment of further waste tobacco material. Since by the presentinvention the calcium oxide may be produced at the nicotine extractionplant at a cost less than that of the cost delivered of the originallime the present invention when employed at the nicotine recovery plantbecomes an important factor in reducing the cost of producing nicotine.Therefore, in this form of the invention the process of recoveringnicotine is in part a cyclic one, since disregarding losses, the lime orother alkaline earth compound used for setting the nicotine free isrepeatedly used over again, so that there is a continuous saving on thecost of such alkaline material.

Where the invention is applied to the production of the new producthereinafter more particularly described, the value of this product,which contains the calcium in the form of a carbonate, is a set off forthe cost of fresh lime for carrying out the nicotine process andtherefore in this way reduces the cost of producing nicotine.

In either form of the invention, the initial steps comprise thetreatment of the waste tobacco material with asolution of analkalineearth compound, usually lime, which may and often does containsome magnesia, then the treatment of the tobacco material with arelatively low degree of heat in a suitable atmosphere to evolve thenicotine, which is carried off and recovered, and to dry the residue ofwaste tobacco material.

The residues thus obtained carry all the calcium and any magnesium whichwas applied to the tobacco material, as well as any calcium or magnesiumwhich was in the tobacco originally, and also carry anappreciable amountof potassium compounds.

The said residues are subjected to a low temperature destructivedistillation process in a suitable kiln to carbonize the vegetablematter and drive off all volatile and low temperature vaporiz-ablematter, burning a portion only of the volatile combustible material inthe kiln, to furnish the heat for the destructive distillation, whileavoiding the combustion of all such volatiles or of any fixed carbon. Inthe best embodiment of the invention the destructive distillation isaccomplished by igniting the tobacco material and burning a portion ofthe volatile matter, with controlled restricted access of air, the hotgases of this combustion passing into contact with fresh tobaccomaterial in the absence of air. The temperature of this destructivedistillation is so controlled that first the volatile components andthose vaporizable at a low temperature are driven off and thereafter theremaining material is car bonized to form a charcoal, it beingimportant, however, and an essential feature of the present inventionthat the material be heated about to the temperature at which potassiumsalts will fuse but most advantageously not above this temperature,whereby there is formed some ash and also a granular mass of carbonconstituting substantially all of the fixed carbon of the tobaccomaterial from Which it was made, this mass of carbon carrying potashderived from the potassium salts of the original vegetable material,this potash not being occluded in the carbon but so carried by thelatter that it is readily extracted, as for example, by percolation, ifdesired. The solids from the destructive distillation step of theprocess are quickly quenched to prevent continuing combustion of thecarbonaceous material when exposed to air, but not sufficiently to coolthe solids to atmospheric temperature, and are, while still warm,subjected to an aqueous extraction step to dissolve out and therebyextract all water-soluble ingredients, these being principally potassiumcompounds-- accompanied by some sodium compounds. Although thesecompounds are mostly salts, for examplecarbonates, there will bepresent, usuallysome. hydroxides, as for example, hydroxides ofpotassium or sodium, or both, with a small amount o potassium cyanidDuring extraction, the solution is separated from the solids, and thenthe solution is subjected to a preliminary concentration step, bybringing it into direct contact with hot combustion gases rich in COwhereby any hydroxides in the solution are converted into carbonates anda considerable portion of the water of the solution s ev porated andcarried off by the d partin gases. Also the potassium cyanide iscarbonated, the acid passing off. Thereafter the concern trated' aqueoussolution is evaporated to recover the potassium and sodium salts insolid form.

The above-mentioned preliminary concentras tion and final evaporation isdone with heat derived from the tobacco material itself. The hot gasesand vapors drivenv off from the destructive distillation zone are passedinto a combustion chamber together with considerable additional air andthereby are completely burned, thus raising the temperature of the gasesand producing a relatively large amount of C02. The hot combustion.gases, richv in CO2, are passed first through the evaporating apparatusthus applying the heat for the final evaporation of the concentratedsolutioh, and then into direct contact with the aqueous solution to beconcentrated. This concentration may be done by passing the hot gases incontact with a rain or traveling film of the aqueous solution so that,the CO2 of the gases may react on the hydroxides and cyanides in thesolution to convert them into, carbonates; may supply heat to thesolution to evaporate some of i s water; and by changing from anunsaturated to a partly or wholly saturated condition may carry off somewater in that The solids from the extraction step, freed irom theirwater-soluble ingredients consists principally of fixed carbon andcarbonates of calcium or magn sium, or bo h, the fixed carbon b inmostly in a ran lar ondition, th granul bein porous and carrying thecarbonates of calcium, or magnesium, or both. As these solids are wetwhen discharged from the extraction step, they are dried by using someof the hot gases derived from the tobacco material.

The dried solid product thus, obtained is a black granular material, hranu e being porous and comprising fixed carbon and carbonate of calciumor carbonate of magnesium, or both sometimes, with small amounts ofother ingredients.

While the percentage composition of this prod uct varies considerably onaccount of variation in the composition of the tobacco waste, a typicalanalysis of such product is as follows:

Percent by weight Carbon 20; Calcium carbonate -g 60 Magnesium carbonate10 Sand, etc -s 10 advantageous as a soil conditioner QIl: account ollts'fiufiy nature, its hi h content of carbonat s of calcium and manesium and h p o nature of the carbon, which in the soil serves to storemoisture and maintain an alkaline c nd t n of u h soil moisture The fineranular c n i i n of the material makes it o ve i nt t ply the materialto the soil by hand or by machinery so as to secure a uniformdistribution of the calcium and magne um carbo at s n e soil. stead,however, of disp sing of th s. n product as a commodity, i may be t e edfurther t burn the carbona es of a cium and ma n t0 oxides, is possibleeconomically because the hired carbon is present in sufiicient amount tofurni h al the hea necessary to drive off the carbonic acid and therebyproduce the required oxides. Therefore, the new product described aboveis ignited and supplied with sufficient air to. burn comp e e y all itsfixed ca n. The re-. sulting calcium and magnesium oxide, with someimpurities, such as sand, is cooled and forms an alkaline product whichmay be used in the nicotine extraction plant for forming the alkalinesolution for treating further waste tobacco mate rial to se fre the itin Since the cost of recovering this alkaline prodnot is less at thenicotine extraction plant than. the cost of fresh lime burned elsewhereand transported to the plant there is a saving in using it, and therebya reduction in the cost of producin n co n The plant for carrying outthe process will now be described.

Eclerrin to the drawings, and particularly to Figs. l and 1A, Aindicates a rotary carbonizing or destructive distillation kiln, into,Which the dried refuse tobacco material from the nicotine extractionplant enters through a pipe H3 at one end, (Big. 3), and from which theresultant solids are discharged at the other end into the conveyor Hwhich carries the solids through a cooling chamber I2, provided with aspraying device 13 and vapor outlet 3 to a distributing conveyor M bywhich the solids, still warm but not incandescent, may be dischargedinto any one of, a series of extraction vats, C. The kiln A, is linedwith fire-brick, as shown in Fig. 5. The gases and vapors from thecarbonizing kiln A are discharged into a combustion chamber, indicatedat Where, by a controlled admission of air through suitable inlets, suchas indicated at b, which may be provided with dampers, not shown, thecombustion is completed and a large amount of hot CG; gas isproduced. Inthe extraction vats C the solids from the, carbonizing lgiln arepercolated with water, which is moved from, vat to vat by a pump,indicated at o. The extracting apparatus will be more fully describedhereinafter. Upon the completion of the extraction step, the solution ispumped off and the solid residues are dischargedin this case by hand,onto an apron c down which the residues slide to a conveyor (1; whichmay be rotated in either direction as required to convey the extractedresidues. to a predryer indicated at, D and comprising a sloping casing;with an enclosed inclined endless belt; [5] which elevates the residuesthrough the casing l6 of the predryer and discharges them to a conveyer11 the residues on the apron being dried by a current of hot combustiogases entering at IT: and rawn through the casing; I6 by a suction fan11 at the lower end, which finally discharges the gases through the fandischarge, pine, l8;- e. conveyor d be; arran ed to (bs harsc: the driedresidues into a suitable container, not shown, these residuesconstituting the new product hereinbefore referred to as suitable forcase hardening and agricultural uses.

Where however, the product is to be burned to completion to produce thecalcium and magnesium oxides, the conveyer :1 is caused to dischargeinto a feeding conveyer e which feeds the dried residues through a gasexit box 2 of a high temperature rotary kiln E. The gas exit boxconnects with a stack F. There may be a duct I1 from the stack F to theinlet H of the predryer D, to utilize the hot gases from the calciningkiln, if desired. The rotary kiln E is lined with fire brick, asindicated at l9, Fig. 6, and has fire brick shelves 2!] for elevatingand dropping the residues. The completely burned product from this kiln,consisting chiefly of calcium and magnesium oxide is discharged to aconveyer g which may discharge the product into either of the two vats GG in which alkaline solution for treating tobacco material may beprepared by adding water and agitating the mixture to form thehydroxides, one vat being used to make such mixture while the other isbeing supplied with the solids by the conveyer g. The alkaline solutionwhen prepared may be run to the liming vats of the nicotine extractionplant by suitable piping, not shown.

The solution of potassium compounds and the like produced at theextraction apparatus may be pumped by the pump to either of two settlingtanks, each forming a part of an apparatus for preliminary concentrationof the liquid from whence it is taken to be evaporated to a sludge, andthen cooled and centrifuged to obtain the crystals. In the bestembodiment of the invention the concentrating and the evaporatingapparatus are in duplicate sets, which work in alternation, so that whenone set is being cleaned, the other may be working.

In the plant illustrated in the drawings, the preliminary concentrationis carried out alternately in that part of the concentration apparatusindicated at H, H each of which, in the present embodiment of theinvention, is similar to a tower gas-scrubber, but contains somemodifications, to be pointed out hereinafter. Each scrubber apparatuscomprises an external casing 2|, of suitable metal, such as iron orsteel, having a chemical-proof lining 22, which is also a poor thermalconductor. This lining may be of tile. To still further retain the heatthe casing may be provided on its exterior with a jacket of thermalinsulating material (not shown). Within the casing is a checker work 23,of chemical brick which rests on a series of arches of the same kind ofbrick, which arches are indicated at 24, Figs. 7 and 10, whereby aninlet chamber 25 is formed at the lower end. The checker Work has itsdiameter reduced at its upper end to form an exit chamber 2% to permitthe free escape of gases from the checker work, the bottom of thischamber being closed at one side only by a masonry floor as indicated at21, Figs. 7 and 8,

' at which side a tight vertical baffle wall 28, is

provided. The discharge stack connects with the space between the bafflewall and the outer wall. The top of the chamber is closed by a head 29,which may be removed when necessary for repairs or cleaning. Also thecasing is provided with cleaning outlets and caps therefore, asindicated at 30, Fig. 2, to permit access to the various parts of theexit chamber.

The exit chamber is connected by an exhaust pipe is, k to the suctionside of a fan K. K

whose discharge side is connected to a discharge pipe W, W, controlledby an adjustable plate damper k Fig. 2.

The inlet chamber 25 at the bottom of each scrubber of the concentratingapparatus is in communication with the combustion chamber B of thedestructive distillation apparatus, through the tubes of an evaporatingpan L, L one for each concentration apparatus H, H and through asuitable conduit Z, Z The evaporating apparatus is constructed asfollows:

From the combustion chamber B, two flues advantageously of masonry,extend in opposite directions, as indicated at Z Z respectively. Eachflue serves as a header to distribute combustion gases to a series oftubes Z passing through a closed pan which forms the evaporatingchamber, the walls of this pan being indicated at 3!, Fig. 2. The panhas an opening in its top, closed by a tight cover 32. The tubes 1discharge into a header box Z from which the conduit 1, or P, leads thegases to the inlet chamber 25 at the bottom of the scrubber device ofthe respective concentration apparatus, as shown in Fig. 10.

The inlet chamber 25 is liquid tight at its bottom to serve as a catchbasin, and has an outlet connected to piping which will conduct liquidto the corresponding settling tank. Where the scrubber device H or H hasthe bottom of the chamber 25 higher than the top of the evaporating panL, L there may be piping connecting the outlet from the chamber 25 withits respective evaporating pan, but this may be omitted if desired. Alsothere is a connection to the respective settling tank. In the presentembodiment of the invention both sets of piping are shown, and are asfollows: The outlet of the chamber 25 is connected to a T 33. Fig. '7,and to this T is connected a discharge pipe 34 which leads to therespective settling tank, and is provided with a valve 36 as will beclear from Fig. 1. When the valve 36 is open, liquid from the bottom ofthe chamber 25 may flow by gravity to the settling tank. To the T 33,another discharge pipe 35 leading to the top of the correspondingevaporating pan may be provided, as shown in Fig. 1, this pipe having avalve 31. This discharge system consisting of the pipe 35 and its valve3'! for each concentrating apparatus serves only as an emergency deviceand may be omitted. In regular practice the liquid is removed from thesettling tank by a pump which sends it to the evaporating pan through apipe system hereinafter more fully described in connection with thedescription of the settling tanks. The settling tank M, or M has apartition near one end to form a well at that end from which well a pumpN or N may take its supply through a suction pipe 38. The partition isindicated by the dotted line 39 in Fig. l and does not extend the fullheight of the respective tank M or M as shown in Fig. 2. The pump Ndischarges through a discharge or supply pipe 40 into a distributingreservoir P, Fig. '7, this reservoir being omitted from Fig. 1 in ordernot to complicate the showing. The reservoir has an overflow pipe 4| anda slotted main weir partition 42, and cross-partitioning 43, whichtogether form a number of little wells. The weir partition supplies eachone of these wells with liquor from the reservoir through the respectiveweir opening or slot. To the bottoms of the wells are connected a seriesof distributing pipes 44 of various lengths, each provided with adownturned end discharging into its respective portion of the top of thechecker Work,

whereby as the liquid passes down the checker work it will be welldistributed and on account of the staggered relation of the bricks inthe checker work, will form a large series of downflowing films andrain, the liquid as it travels downward being brought into intimatecontact with the hot gases of combustion, which travel upward, theliquid finally reaching the bottom of the concentration apparatus andduring the normal operation of the apparatus, passing back to therespective settling tank,,through the pipe 34 to be again lifted by thepump N or N to the top of the concentration apparatus, thus making acontinuous circuit repeatedly.

To the outlet pipe ll! of the pump N is connected a bleeder pipe 45,provided with a valve '16, this pipe extending to and connecting withthe pipe 35 beyond its valve 3?, as for example, at the T 41. When it isdesired to discharge liquid from the settling tank M to thecorresponding evaporator L, the valve 46 may be opened, and valve 40 onpipe 40 may be closed whereupon the pump N will discharge direct to theevaporator, it being understood that the valve 31 is normally closed. Incase, however, it is desired to discharge directly from the bottom ofthe chamber 25 to the evaporator L the valve 3'5 is opened and the valve46is kept closed.

The settling tanks Mare supplied with liquid from the percolators by apipe C connected to the discharge side of the pump 0, suitable valves 0C being provided as shown in Figs. 1 and la.

The percolators C are alike. Each consists of a vat having a falsebottom consisting of two screens, the upper one 52 of finermeshrthan thelower one 53, whereby a chamber is formed below the screens, as shown inFig. 4. The solids to be treated rest on the uppermost screen 52. Asbefore described, these solids are supplied to the respective vats bythe conveyor I4 which is of the usual distributing conveyer type soarranged that its bottom can be opened opposite any vat, or closed toallow the material in the conveyer to be passed along further. As thedetails of these distributing conveyors are old and well known, thesedetails have not been illustrated in the drawings. The lower screen 53is made strong enough to support the maximum load of carbonaceousmaterial which may be placed in the vat, without any appreciablesagging, the upper one being of fineenough mesh to prevent the passageof any appreciable amount of fine solids, it being expected that duringthe percolation step the lower part of the bed of material resting onthe screen will act as a filter bed to prevent the finer dusts frompassing through the screens. An outlet 0 is connected to the chamberbeneath the screen, the outlet from each vat being connected to thecommon suction pipe 0 of the pump 6. Each outletpipe c -is provided witha valve, as indicated at 0 provided with an individual supply pipe 0provided with a valve 0 these supply pipes. being connectedto thedischarge pipe 0 of the pump 0. By means of the pump and the connectionsdescribed, the. solution in anyvat can be pumped to any other vat, bysuitable adjustment of the valves, as will be obvious to, those skilledin the art.

In order to provide a supply of water for the vats, each is providedwith a water supply pipe, as indicated at c which branch from a watermain 0 suitable valves 0 being employed to control the individual watersupply pipe as indicated. In the embodiment shown in the draw- Each vatis ings a distributing device or sprinkler c is provided for each vat,each consisting of a central pipe and a plurality of branch pipes orarms, the latter being perforated on their undersides. By means of thesesprinklers, the water from the water main may be sprinkled or welldistributed over the carbonized residues in the vats when firstsupplying the water to the vats. Then the sprinkler may be disconnectedfrom the water supply system and connected to the pipe 0 removing thedown-turned nozzle if it is in place, and therefore, the sprinkler canserve to distribute any solution pumped to a vat from another vat.

In practice it has been found that such a sprinkler device is not reallynecessary, although perhaps a slight advantage. This is because thecarbonized material from the carbonizing kiln ,is so porous that anymeans of filling the water into the vat on top of the carbonizedmaterial is entirely satisfactory on account of the almost immediatesolution of the potassium and other soluble compounds as soon as thesolid material is immersed.

When a vat is charged with water, and has stood for a few minutes, thesolution may be drawn off and pumped to another vat Whose solution hasbeen withdrawn. In this way the solution is pumped from vat to vat inseries, grad-l ually increasing the concentration of the solution to thedesired maximum. When this point has been reached the solution in itsdesired maximum concentration may be pumped off and discharged tosuitable storage tanks until the concentrating apparatus requires asupply, or if the settling tanks are large enough, the concentratedsolution may be pumped to them. In the draw-.

ings, the discharge side of the pump 0 is provided with a discharge pipeC! which has branches 0 each having a valve whereby the solution may bepumped to either one or both of the two settling tanks M, M Fig. 1.

The vats may be operated in series as follows: One vat having beenfilled with carbonized residues, is supplied with freshwater. Then thesolution may bepumped to the vat next to it, which had been filled withcarbonized residues, and fresh water supplied to the first. The solutionin the second vat may then be pumped to a third vat containing freshcarbonized residues, the weaker solution in the first vat pumped to thesecond vat, and fresh water again supplied to the first vat. This methodof moving the solutions forward and supplying the first vat with freshwater is continued until the carbonized residues in the first vat havebeen supplied, or washed, with about five charges of fresh water.strongest solution may then be pumped off to be concentrated; theseveral weaker solutions moved successively to the next vat ahead, andthe extracted carbonized residues may then be discharged from the firstvat. This same vat is then charged again with fresh carbonizedresiduesand supplied with the stronger solution in the circuit; the other weakersolutions moved forward successively, and fresh water supplied to theweakest. In practice the initial solution supplied to each freshlyfilled vat may be pumped off to be further concentrated, the washingsmay consist of several successively weaker solutions with a finalwashing of fresh water, and the operations may be so timed that freshcarbonized residues are supplied to one vat during the period that theextracted carbonized residues are The being discharged from the vat nextin line. the vats the solids are treated with water to extract all theirwater-soluble contents, principally potassium and sodium salts with somepotassium and sodium hydroxides including, as a particularly dangerousingredient, a very small proportion of potassium cyanide. By pumping thesolution from one vat to another, the concentration of the solution isgradually increased, until finally the solution is removed and put instorage for further treatment or sent to the proper settling tank M or Mof the preliminary concentrating apparatus. Usually there are some finesolids in suspension in the solution and these will tend to settle outin the settling tank as a sludge, which can be shoveled out from time totime and can be returned to the extracting or percolating apparatus.

As the settling tank is gradually filled it finally overflows itspartition 39 and fills the small compartment connected with the pump.Let it be assumed that the concentration apparatus comprising thesettling tank M and the scrubber H is to be used first. Valves 46 and 31being closed, the fan K is put in operation. This draws the hot gaseousproducts of combustion from the combustion chamber B, through the flue 1through the tubes Z of the evaporator L, through the duct 1, and throughthe checker work of the scrubber H to the top of the latter, the fandischarging through the fan outlet 70 to the atmosphere. The pump N isset in operation simultaneously with the starting of the fan K wherebythe liquid solution from the tank M is pumped to the distributor tank Pand from there fed to the various branch pipes 44 which distribute thesolution, in a reasonable approach to uniformity, over the top of thechecker work, down which it travels, sometimes as films on the bricks,sometimes as a shower or rain when falling through the spaces betweenthe bricks, owing to the staggered relation of the bricks in the variouscourses. On its way down, the finely subdivided solution meets theascending current of hot gases, which are rich in CO2. As a result thewater in the solution is gradually evaporated as it descends, and at thesame time any inorganic compounds in the solution which will react withCO2 are carbonated, such for example, as potassium hydroxide andparticularly potassium cyanide. The latter has its acid driven off butin such great dilution with the large amount of gaseous products whichescape from the scrubber, that no serious effects will result from thedischarge of such mixture into the open air.

The solution, increasing in concentration of inorganic salts as ittravels downward because of the removal of its moisture by the hotcombustion gases, finally reaches the bottom of the scrubber H andpasses back to its settling tank M'through the pipe 34, the valve 36being open at this time. The returning concentrate-d solution depositsin the settling tank as sediment the dust which it has washed out of thegases coming from the combustion chamber and causes a continual flow ofthe upper layer of clean liquid over the partition to the pump suction.In this Way there is a continuous circulation of the liquid through thescrubber and settling tank, with a continuous removal of values from thegases, a continuous carbonation of those compounds in the solution whichcan be carbonated, and a continuous evaporation and removal of waterfrom the solution, thereby rapidly concentrating the solution to thedesired point. When the solution has reached a concentration where it isdifiicult to handle further by the pump and before it has reached thestage of depositing solids in the scrubber, the process is stopped in.the concentrating apparatus at that time in use, and the otherconcentrating apparatus is started. This is done by stopping the fan Kand simultaneously starting the fan K and the pump N the valve 46 beingopened so that the pump N will pump the concentrated solution fromsettling tank M to the evaporating pan L, the latter having been drainedof any fresh water it contains if such were used at the initialoperation to prevent burning of the tubes in such pan.

When the pan L is filled with solution from the tank M it stands out ofoperation, while the other concentrating apparatus is operating in thesame manner as hereinbefore described. in connection with the firstmentioned concentrating apparatus. In other words the two concentratingapparatuses and the respective evaporating pans work in alternation,thereby maintaining a substantially continuous discharge of the gasesfrom the combustion chamber B.

While the first mentioned concentrating apparatus is out of operation,its settling tank M receives a new charge of weak solution from theextractors, or from a storage tank, if such is used, and is ready foroperation again as soon 9 as the other concentrating apparatus hascompleted its work and is ready to be put out of operation.

On the next operation of the apparatus including the tank M and scrubberH, the gases from the combustion chamber B on their way to the scrubberH pass through the tubes of the evaporating pan L which is now chargedwith a strong solution. Thereupon, the evaporator operates toconcentrate the strong solution to crystallize out the salts. Theevaporating pans are so proportioned that they will hold all the strongsolution made at the prior run of the associated concentrating apparatusand will evaporate its charge tothe full extent before the apparatuswith which it is associated is shut down. When this occurs, theevaporating pan is discharged by allowing its contents to flow,intermittently, to the centrifuge F, the solids for the most part beingremoved from the pan by stirring so that they are carried in suspensionto the centrifuge. Any solids which do not flow out may be removed fromthe pan by suitable means, as by scoops or shovels, and thus transferredto the centrifuge.

The centrifuge F is provided with a suitable electric motor for drivingit. The pipes for withdrawing any suspension or sludge in the respectiveevaporators are indicated at 0 p respectively, each pipe beingcontrolled by a valve as shown. The mother liquor from the centrifuge,freed from any solids which can be thrownout by centrifuge action, isdischarged by gravity to a small tank, not shown, from where it may bepumped to a storage tank for cooling to deposit further solid salt, orto the evaporator then in use, or, as indicated in Fig. 1, back into thesystem by way of the settling tank, through pipe f and pump N.

The solids from the evaporating pan after passing through the centrifugeare in excellent marketable condition, being relatively dry salts freefrom deliquescent material and from cyanides. 'The principal and mostvaluable constituents are potassium salts which can be marketed withoutfurther refining at a price above the cost of production, so that theprocess is commercially satisfactory.

Referring again to'the extractors, the solids removed from the vats arewet granular ma terial containing very porous fixed carbon, in thegranules of which is disseminated alkaline earth compounds such ascalcium or magnesium compounds, practically all in the form of car'-bonate. This product when dried is very suitable as a soil conditionerfor agricultural purposes and as a case hardening material, ashercinbefore explained. To dry the product it is fed onto the "travelingbelt I5 of the predryer and carried along through the atmosphere of hotgases, which can be supplied either from the combustion chamber, B,through the duct H or from the calcining kiln E, if the latter is inuse, through the duct H The dried product is deposited by the belt inthe conveyer (P, which may deposit the product in a suitable receptacle.

Where, however, it is desired to treat the prodnot further to calcinethe alkaline earth carbonate to oxides, the conveyer d is arranged to'discharge into feed conveyer e, which continuously feeds the material tothe rotary calcining kiln.

As the granular carbonaceous material travels down the inclined rotarykiln, which is rotated through the usual ring gear as shown in Fig. 1,the carbon is ignited and gradually consumed. The ignition is startedinitially by an oil burner or torch, not shown. Thereafter theincandescent material in the kiln serves to ignite the incomingmaterial. Air is supplied in sufficient quantity at the lower end of thekiln to maintain an intense heat which is sufficient to convert thecarbonates of calcium and magnesium to oxides. It is to be noted thatthe quantity of fixed carbon is more than sufficient to convert all thecarbonates to oxide and the excess is sufiicient to predry the wetsolids on their way to the calciningkiln. Hence, it becomes possible torecover the oxides of calcium and magnesium which were used in thenicotine extraction process, so that such oxides may be converted tohydroxides and again used in the recovery of further nicotine, thisbeing done at so low a cost that there is an appreciable saving in thecost of the lime as prepared in this way, which serves to reduce thecost of nicotine production.

The ash is discharged from the calcining kiln to one or the other of twovats, indicated at G and G When the ash, which is chiefly calcium oxide,is to be used for liming waste tobacco material at the extraction plant,water may be supplied to the vat G or G as soon as it has received asufiicient charge of ash, and the solution thus made is run off to theliming vats of the nicotine extraction plant, thereby completing thecycle of operations of such lime.

When one of the vats is being used for making solution, the other isbeing charged with ash from the kiln, the two vats working alternately.

Although in the specific description of the process and apparatus thestarting material has been specified as waste tobacco, there are someother starting materials which have characteristics similar to those oftobacco which may be used. All such materials suitable for treatment bythe steps of the process must have a relatively high percentage ofpotassium compounds and of constituents which when heated will evolvecombus 'plant material having a relatively high content of potassiumcompounds and also of constituents which when heated will evolve arelatively large amount of volatile combustible material, which consistsin progressively feeding such material through a heated zone whosetemperature increases in the direction of travel of the material to apoint whereby volatile combustible products are evolved, burning aportion only of said volatile combustible products in contact with theplant material, with controlled restricted access of air, to carbonizethe material as it reaches the hottest part of the zone, leading off theproducts of such combustion mixed with the unburned portion of thevolatile combustible material, supplying additional air to such mixturewhile it is still hot, to complete the combustion of the mixture out ofcontact with the plant material and produce high temperature combustionproducts rich in CO2, progressively removing the carbonized material assoon as it has been freed of its volatiles and before its fixed carbonis consumed, extracting the Water-soluble compounds from the -carbonizedproducts, separating the solution from the solids, and driving off themoisture of the solution from its solids by the heat of said hotcombustion products.

2. The process of recovering values from landplant material having arelatively high content of potassium compounds and also of constituentswhich when heated will evolve a relatively large amount of volatilecombustible material, which consists in progressively feeding suchmaterial through a heated zone whose temperature increases in thedirection of travel of the material to a point whereby combustibleproducts are evolved, burning a portion only of said volatilecombustible products in contact with the plant material, with controlledrestricted access of air, to carbonize the material as it reaches thehottest part of the zone, leading off the products of such combustionmixed with the unburned portion of the volatile combustible material,supplying additional air to such mixture while it is still hot, tocomplete the combustion of the mixture out of contact with the plantmaterial and produce high temperature combustion products rich in CO2,progressively removing the carbonized material as soon as it has beenfreed of its volatiles and before its fixed carbon is consumed,subjecting the said carbonized material to the action of water toextract the water-soluble compounds from the carbonized products,separating the solution thus obtained from the solids, bringing the hotcombustion products aforesaid into direct contact with the solution insubdivided form whereby the CO2 reacts with certain of the inorganiccompounds in the solution to carbonate the same, and water is driven offfrom the solution to concentrate it, and finally evaporating theconcentrated solution to crystallize out the salts.

3. The process of recovering values from waste tobacco residues from anicotine extraction plant, said residues containing alkaline earthcompounds, which consists in progressively feeding such residues througha heated zone whose temperature increases in the direction of travel ofthe residues to a point whereby volatile combustible products areevolved, burning a portion only of said volatile combustible products incontact with the residues, with controlled restricted access of air, tocarbonize the residues as they reach the hottest part of the zone,leading oi the products of such combustion mixed with the unburnedportion of the volatile combustible material, supplying additional airto such mixture while it is still hot, to complete the combustion of themixture out of contact with the residues and produce high temperaturecombustion products rich in CO2, progressively removing the carbonizedmaterial as soon as it has been freed of its volatiles and before itsfixed carbon is consumed, subjecting the said carbonized products to theaction of water to extract the Water-soluble compounds from thecarbonized products, separating the solution from the solids, drivingoff the moisture of the solution from its solids by the heat of said hotcombustion products, drying the solids from the extraction step,igniting said solids with a free sup-ply of air to burn all the fixedcarbon and thereby convert the alkaline earth compounds to oxides andprovide an excess of heat and utilizing the excess heat to dry furthersolids obtained from the extraction step.

ROBERT E. ARNOLD.

